We propose to study brain glutamate and GABA turnover inpatients with epilepsy using combined lH and 13C NMRS. The responses to two novel anti-epileptic drugs will serve as probes to clarify the metabolic response to increased levels of GABA. We continue to investigate the relationship between in vivo rate of GABA synthesis, glutamic acid and decarboxylase (GAD) activity, and GABA concentration. Assess the effects of increased Human Brain GABA on the expression of Benodiazapine receptors as a marker for GABA-A receptors using serial single photon emission computer tomography (SPECT) and 1H Magnetic Resonance Spectroscopy (1H NMRS). Explore the mechanisms associated with the increase in Human Brain GABA following Gabapentin administration using serial measurements of the rate of cerebral glutamate, GABA, and glutamine turnover before and after the administration of Gabapentin.